I tried connecting directly speakers to sony led TV but its not working.
Do I need any additional equipement to connect external speakers to TV ?

It depends on the speakers. If you are using a soundbar or computer speakers, then you shouldn't need anything additional. Basically those types of speakers already have some kind of amplifier built into them and usually plug into your electrical for power.

If you are trying to connect just stand alone speakers with no additional amplifier (or an A/V receiver), then it will not work.

Provide us makes and models of your equipment and we can tell you the best method to go about connecting your equipment. Also, if you need to purchase any additional equipment please provide details about what features you would like from the additional equipment so we can give you better recommendations.

The speakers that I am trying to connect are old types with two copper wires coming out of it.How do I connect it to my bravia?

A Receiver or an Amp would work.
If you Have a Satellite or Cable Box, you could hook to the audio output.
Or out of The Bravia and then go into the menu to select Fixed or Variable Output.

How would you choose an amplifier?Is there any particular rating that I should look for?

Most any would work, just depends on your Wallet, and how Good you want your sound.

Can you suggest me some standard specs?

You will also need Speakers, If you have none now, then:
Back in a minute

Are you planning on spending about $50, $500, or $5000?